Hi aros2,
Apologies for the delay in replying, and great work solving the issue! I'm not totally sure why the auto-calculate code was causing the issue (maybe it was setting the bone length to zero? Maybe something since I wrote it changed how the calculation works?) but I'm glad that you were able to solve it! And thank you for sharing the solution here so others can benefit from it as well in case they also run into the issue.
Thanks again,
TwistedTwigleg